Wetting agent



July 27, 1954 PL EBAUGH ETAL WETTING AGENT Original Filed Oct. 12, 1945INVENTORS PAUL EBAUGH BY LEON T. PIEKARSKI Patented July 27, 1954 WETTING AGENT Paul Ebaugh, State College, Pa., and Leon T. Piekarski,Schenectady, N. Y., assignors to the United States of America asrepresented by the Secretary of the Navy Application May 27, 1949,Serial No. 95,867

(01. ISL-0.5)

2 Claims.

This invention relates to wetting agents and is particularly directed toa wetting agent which is effective for rubber surfaces to be immersed inwater.

In the use of transducers for underwater sound signaling it isfrequently desirable to provide a rubber face for the transducerdiaphragm which is in direct contact with the water since rubbercompounds can be prepared to have essentially the same soundtransmission characteristics as water. One of the difliculties which hasbeen encountered in the calibration and use of rubber-faced transducersis the fact that air bubbles cling to the surface of the transducer asit is immersed in the water and are likely to remain there for a longperiod of time. While the air bubbles are present the sound transmissionand receiving characteristics of the transducer cannot be takenaccurately since the air-water and air-rubber interfaces representdefinite barriers for the transmission of sound waves.

It has been the practice to scrub the transducers prior to immersion andto use certain wetting agents which were calculated to disperse the airbubbles. In some instances this procedure has not been eiiective becausethe wetting agents do not remain on the surface of the rubber but becomedissolved in the water leaving the face of the transducer in imperfectcontact with the medium.

The present invention has for its primary object to overcome thediiiiculty above set forth and to provide a wetting agent which becomesadsorbed on the rubber surface to present a continuous hydrophilicsurface to the water.

Another object of the invention is to provide an actively chargedwetting agent which will increase the interfacial tension between arubber surface and a surrounding liquid medium.

Other objects and advantages of the invention will become apparent fromthe following description in which a preferred form of the invention isdisclosed and from the accompanying drawing, the single figure of whichshows a typical embodiment of the features of the present invention.

With reference now to the figure, a cup-shaped casing l of steel or thelike has its open end covered with a vibratile diaphragm 2 of steel orother suitable material. Diaphragm 2 is held in place on the casing by asuitable means such as a clamping ring 3 and bolts 4. To produce orutilize vibrations of diaphragm 2, magnetostrictive devices =5-5 areattached to diaphragm 2 and surrounded in part by coils 1-4. Coils 'l-7are operative with electrical connections (not shown) which are broughtthrough suitable water tight feed-through devices placed in the wall ofcasing I.

Surrounding the foregoing assembly is a corrosion resistant layer orcoating i! of rubber which may be applied by one of several conventionalWays, typically by vulcanization.

Adsorbed on the external surface of the coating 9, particularly thatportion thereof which covers the diaphragm 2, is a thin layer it oftriethanolamine acetate. This layer is of such minute thickness as to beimpossible to show to reasonable proportion in the figure, however dueto a phenomenon involving surface adsorption, this material remains onthe surface of the rubber for prolonged periods of time and provides aVast improvement in the wettability characteristics of the rubbercoating.

The wetting agent of the present invention relies for its effectivenesson the fact that neutral materials such as rubber acquire a negativecharge when immersed in an aqueous medium. A wetting agent which isinitially positively charged or cation-active will absorb on thenegatively charged rubber face and cause the rubber face to becomecompletely wetted. One compound which has been found satisfactory forthis purpose is triethanolamine acetate which can be prepared by mixingone part of acetic acid to two and one half parts by weight oftriethanolamine. An excess of acetic acid may be used withoutdetrimental effect.

Triethanolamine has the structural formula:

OH-CHr-CHz OHCH2CH2--N OH-CHPCHI This substance when combined withacetic acid (CH3COOH) results in an acetate having the followingstructural formula:

In aqueous media the hydrogen is closely held because the nitrogen is ina pentavalent state and the salt dissociates into the acetate radicaland the positively charged ammonium complex. This latter adsorbs ontothe surface of the rubber and forms a hydrophilic surface thereon. Therubber surface, so coated, is readily wetted by water due to thepresence of the hydrophilic hydroxyl radicals in the compound which havebecome adsorbed.

In use the rubber surface is cleaned to assure the removal of oilymaterials and thoroughly rinsed to assure the absence of anioniccompounds such as soaps and mild cleaning acids. The presence of ananionic compound will, of course, reduce the effectiveness of thetriethanolamine wetting agent.

While the present invention has been found effective the advantagesgained by its use can be increased if temperature equilibrium can beestablished between the transducer and water prior to immersion.However, the immersion of a warm transducer in cold water will result,when first prepared as above suggested, in the presence of small bubbleshaving a contact angle with the rubber surface which is so large thatslightly mechanical agitation will release the bubbles. Thus even a verywarm transducer which has been coated with our Wetting agent is usuallycleaned of all air bubbles simply by rotating it or otherwise moving itin water immediately after immersion.

Acetic acid is the preferred source of hydro gen ions, but other acidssuch as formic, hydrobrornic and hydrochloric acids may be used in thesame manner.

While the present invention is particularly effective on rubber surfacesit may also be used on other surfaces which acquire a similarly negativecharge when immersed in water, such as synthetic rubber, artificialresins, glass and sulphur. While a specific compound has been disclosed,other compounds of an equivalent nature may be used without departingfrom the invention as defined in the appended claims.

This application is a division of application Serial No. 622,078, filedOctober 12, 1945, for Wetting Agent, but now abandoned.

What is claimed is:

1. A transducer unit for underwater sound signalling, comprising a soundactuatable diaphragm, a rubber coating on said diaphragm having normallya negative charge when immersed in water, and a coating oftriethanolamine acetate on said rubber coating, said triethanolamineacetate coating disassociating into an acetate radical and a positivelycharged ammonium complex which adsorbs on said rubber coating thereby topresent a continuous hydrophilic surface to an aqueous medium.

2. A transducer unit for underwater sound signalling, comprising a soundactuatable diaphragm, a coating on the diaphragm surface of rubber-likematerial having normally a negative electric charge when immersed inWater, and an additional coating on the rubber-like material coating ofa compound having a positively charged hydroxyl containing radical, saidcompound being formed of triethanolamine and any one or" the acid groupconsisting of acetic acid, formic acid, hydrochloric acid andhydrobromic acid, said additional coating adsorbing on said rubber-likematerial thereby to present a continuous hydrophilic surface to saidwater.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,176,326 Sutline Mar. 21, 1916 1,890,158 Lindstaedt Dec. 6,1932 2,094,609 Kritchevsky Oct. 5, 1937 2,200,184 Morgan May 7, 19402,206,517 Stefiens July 2, 1940 2,214,646 Walker Sept. 10, 19402,279,860 Crawford Apr. 14, 1942 2,421,079 Narcus May 27, 1947 2,444,507Hanson July 6, 1948 2,496,060 Mell et al Jan. 31, 1950

1. A TRANSDUCER UNIT FOR UNDERWATER SOUND SIGNALLING, COMPRISING A SOUNDACTUATABLE DIAPHRAGM, A RUBBER COATING ON SAID DIAPHRAGM HAVING NORMALLYA NEGATIVE CHARGE WHEN IMMERSED IN WATER, AND A COATING OFTRIETHANOLAMINED ACETATE ON SAID RUBBER COATING, SAID TRIETHANOLAMINEACETATE COATING DISASSOCIATING INTO AN ACETATE RADICAL AND A POSITIVELYCHARGED AMMONIUM COMPLEX WHICH ADSORBS ON SAID RUBBERCOATING THEREBY TOPRESENT A CONTINUOUS HYDROPHILIC SURFACE TO AN AQUEOUS MEDIUM.